1. Field of the Invention
The present invention relates to aqueous dispersions of water-soluble polymers of N-vinylcarboxamides, processes for the preparation of the dispersions in the presence of stabilizers and the use of the dispersions as drainage aids, flocculants and retention aids, as wet and dry strength agents and as fixing agents in papermaking.
2. Description of the Background
EP-B-0.814 099 discloses a process for the preparation of aqueous dispersions of a water-soluble cationic polymer, in which an aqueous dispersion of a polymer containing vinylformamide units, which dispersion contains neutral salts, is hydrolyzed with an acid in an aqueous medium with addition of nitrates. The resulting aqueous dispersions of polymers containing vinylamine units have a high neutral salt content.
WO-A-97/30094 discloses a process for the preparation of dispersions of water-soluble cationic vinyl polymers. The polymerization of the water-soluble monomers is effected in aqueous salt solutions in the presence of stabilizers which consist of a water-soluble graft copolymer which contains polyethylene oxide as a grafting base and cationic vinyl monomers as grafted-on side chains.
WO-A-98/54234 discloses aqueous dispersions of water-soluble N-vinylcarboxamides. The dispersions are prepared by polymerizing N-vinylcarboxamides in an aqueous medium in the presence of water-soluble salts and water-soluble polymeric stabilizers. The polymeric stabilizers used are, for example, polyvinyl alcohol and partially hydrolyzed polyvinyl acetates.
WO-A-00/27893 relates to aqueous dispersions of water-soluble polymers of N-vinylcarboxamides, processes for their preparation and their use as drainage aids, flocculants and retention aids, as wet and dry strength agents and as fixing agents in papermaking. The polymeric dispersants, e.g. polyethylene glycol, polypropylene glycol, polyvinyl acetate, polyvinyl alcohol, polyvinylpyridine, polyvinylimidazole and polydiallyldimethylammonium chloride, are used for stabilizing the dispersions.